Last Updated on December 7, 2023
Chances are, if you’re a car owner, you’ve heard of oil consumption. You might even know that it’s bad for your engine. But what is oil consumption, exactly?
Oil consumption is when the engine oil enters the combustion chamber, and is burned off rather than returned to the oil pan for further lubrication. Small amounts of oil consumption are common. However, if your car has lost significant amounts of oil before the next oil change, then this is an indication of excessive oil consumption. If ignored, excessive oil consumption can lead to serious engine damage.
In this guide, we’ll answer the most commonly asked questions and more about oil consumption. We’ll also help you determine whether or not your car has a problem with oil consumption.
So read on to learn everything you need to know about this serious issue!
When is Oil Consumption a Problem?
The issue of oil consumption is something that can be quite frustrating for car owners. More often than not, manufacturers don’t provide uniform guidance on this issue.
As a general rule, however, if an engine requires a quart of oil every 3,000 miles or less, that could be a sign of excessive consumption.
This level of oil consumption is a problem that will damage not only valve guides and piston rings but also lead to increased fuel use and reduced fuel economy.
What Causes Oil Consumption?
The most common factor for engine oil consumption are worn valve stems, bad seals, and worn or cracked piston rings. All of these can allow oil to seep into the combustion chambers of the engine.
In older cars, especially older diesel engines, as the engine ages the wear and tear of components like the valve cover gasket, intake manifold, and PCV valve (Positive Crankcase Ventilation) can exacerbate the issue.
Modern engines, however, with their advanced engine design and use of higher quality oil, such as fully-synthetic oils, tend to have lower consumption.
What is Excessive Oil Consumption?
Excess oil consumption is anything above an acceptable range during normal operating conditions. Each engine will have a natural and acceptable amount of consumption, which you do not need to worry about.
Generally, most auto manufacturers consider it normal for an engine to consume up to about one quart (approximately 0.95 liters) of oil every 1,000 to 2,000 miles (1,600 to 3,200 kilometers).
Any consumption above these given levels is excess consumption and should be addressed. For modern vehicles, extended service intervals mean that engines are designed to use less oil, and oil change intervals can be longer.
What Are the Effects of Engine Oil Entering the Combustion Chamber?
Engine oil is a hydrocarbon, and when presented in the combustion chamber during the combustion cycle, it ignites and burns as any other hydrocarbon. However, due to the chemical nature of oil, it is more viscous and denser than gasoline.
This means it burns slower and generates heat over a longer period of time. Because of these characteristics, engine oil contributes practically nothing to the combustion process, and only generates heat in the exhaust system.
It does consume some of the oxygen in the combustion chamber, thereby reducing both ignition and combustion efficiency. This in turn increases emissions, which causes the fuel management system to introduce a different and most often non-optimal fuel-to-air ratio during the next cycle.
Optimum combustion depends on the correct fuel/air ratio in order to provide a near stoichiometric mixture. The oxygen sensors monitor unburned oxygen in the exhaust gases and send this information to the engine control module, which then uses this information to determine if the fuel mixture is rich (too much fuel) or lean (not enough fuel) and adjusts the fuel/air mixture as necessary.
The oxygen sensors also measure oxygen levels after the exhaust reacts with the catalytic converter, to help the engine run efficiently and to minimize emissions.
The catalytic converters are emission control devices designed to convert toxic pollutants contained in exhaust gases to less toxic pollutants by catalyzing a redox reaction (oxidation or reduction).
Is it Normal For Turbocharged Engines to Consume Oil?
Turbocharged engines, which are known for better power and efficiency, often use a bit more oil than regular engines. Even when using fully-synthetic oils.
This happens because they work at higher temperatures and pressures, which can cause more oil to burn or get used up. The turbocharger’s design, especially the oil-cooled parts, also plays a role in this.
However, if a turbocharged engine is using too much oil, it might mean there are problems like worn-out seals or damaged parts.
So, if you have a car with a turbocharged engine, it’s a good idea to regularly check the oil level and follow the recommended schedule for oil changes. This way, you can catch any big changes in oil use early on and avoid bigger engine problems.
Effects of Excessive Oil Consumption
Worn valve stems, guides, and seals can all allow oil to seep into combustion chambers. This is often a result of prematurely worn components that have been neglected over time–the byproduct being burnt fuel with little power resulting in low engine performance.
Long-term uneven wear on different engine parts could lead up to an even bigger problem down the road–such as seal failure leading to more serious issues like major engine damage.
Why No Recall for Oil Consumption?
The National Highway Traffic Safety Administration has declared that they will not recall a car due to excessive oil consumption.
However, this decision often depends on the specific circumstances and the extent to which the oil consumption affects the safety and performance of the vehicle.
Oil is an essential, yet often overlooked part of the engine. If you don’t keep your oil at the right level, your car will run poorly or stop running completely in some cases. The best way to ensure your engine doesn’t break down is to take preventative measures and keep an eye on the oil level.
Regular oil changes, using the correct oil viscosity, and addressing mechanical problems promptly can significantly reduce the risk of excessive oil consumption and expensive repairs.
Have you checked your car’s oil lately?